Variable height beds of the type to which the present invention is related, have been known for some time. Examples of the prior art may be found in U.S. Pat. No. 4,271,830 Moon of June 9, 1981; U.S. Pat. No. 2,280,444 Neunherz, Apr. 21, 1942 and U.S. Pat. No. 3,305,876 Hutt, Feb. 28, 1967 and U.S. Pat. No. 1,890,177 Derry, Dec. 6, 1932.
Further examples of beds having a variable height features may be found in U.S. Pat. No. 4,398,313 Mitchell, Aug. 16, 1983; U.S. Pat. No. 4,556,198 Tominaga, Dec. 3, 1985 and U.S. Pat. No. 3,304,116 Stryker, Feb. 14, 1967.
While many of the above-mentioned patent specifications disclose desirable features, hospital research bodies and nursing staff are always striving to locate bed structures having the most functional features with respect to patient comfort, care and safety and ease of operation by attendant staff.
Beds used in general care areas of hospitals and long term care areas of extended care facilities and the like normally incorporate a multi-section mattress surface and the head and knee portions, generally referred to as gatches, must be able to tilt to different angles and the height of the bed should be variable.
The features most desired in a bed structure by nursing and attendant staff is a bed having a variable height supporting surface which can be lowered to a minimum height of approximately ten inches above the floor; a maximum height of approximately twenty-nine inches or more above the floor; substantial clearance under the midsection of the bed; means for elevating the support surface without having to resort to hand crank operation; guard rail structures which could be located totally out of the way of the sides of the support structure when those guard rails are not needed and some means to securely immobilize the bed against moving or shifting and which could be operable at any bed height.
Attempts to modify existing bed structures as generally known in the industry, were unsuccessful in meeting the above mentioned features and functions. A variety of problems arose when such modifications were attempted. For example, when the elevation of a bed in its lowermost position was decreased, the bed no longer rose high enough for other functions. Under-bed clearance space was lost and guard rails no longer were functional in the lowermost position. Moreover, head and knee gatch operating mechanisms hit the floor or supporting surface and the ability to tilt portions of the bed were no longer available. The lift operating cranks became too low to conveniently operate; and some designs, when modified, ended up being excessive in longitudinal movement.
Beds of the structure using an X-type or scissor form of lift have inherently very poor under-bed clearance when the bed is moved to its lowermost position. Such beds need to be raised to a considerable portion of their maximum height before achieving the desired under-bed clearance.
Considering for example the patent to Moon U.S. Pat. No. 4,271,830, the structure shown therein is a chiropractic table and does not have any castor wheels, guard rails or movable head and knee gatches. The integration of such units into the present invention is important and are required functional features in the area to which the invention relates. To attempt to modify a structure such as in the Moon patent to meet the above-mentioned functions and features would result in nothing short of a complete redesign of the Moon patent structure. For example, the table of the Moon patent has no clearance space underneath the structure and there is no easy means for making such modifications for such clearance. Certain parts for the elevating mechanism of the Moon device occupy this space. A further problem is that the table of the device in the Moon patent appears to be incapable of moving from a low elevation point of ten inches to a high elevation point of approximately twenty-nine inches.